UQCRQ encodes a ubiquinone-binding protein of low molecular mass. This protein is a small core-associated protein and a subunit of ubiquinol-cytochrome c reductase complex III, which is part of the mitochondrial respiratory chain.Ubiquinone is an essential component of the mitochondrial electron transfer system. UQCRQ is a ubiquinone-binding protein localized to the cytochrome bc1 region of the mitochondrial respiratory chain.